Fracture mechanics analysis of the dentine-luting cement interface

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Adhesive Dentistry

Background:

• Dental luting cements are critical for prosthetic restorations.
• Understanding the mechanical properties of cement-dentine interfaces is essential for clinical longevity.
• Thin cement layers are commonly used in clinical practice.

Purpose of the Study:

• To determine the fracture toughness of adhesive interfaces between dentine and thin layers of dental luting cements.
• To compare the fracture toughness of a conventional glass-ionomer (Fuji 1), a resin-modified glass-ionomer (Fuji Plus), and a compomer cement (DyractCem).

Main Methods:

• Manufacture of miniature short-bar chevron notch specimens with 40 µm cement layers between bovine dentine blocks.
• Testing of interfacial fracture toughness (K(IC)) using standardized methods.
• Analysis of crack propagation using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Main Results:

• Fracture toughness values (median, range MN/m³/²): Fuji 1 (0.152, 0.14-0.16), Fuji Plus (0.306, 0.27-0.37), DyractCem (0.351, 0.31-0.37).
• Fuji 1 exhibited significantly lower fracture toughness compared to Fuji Plus and DyractCem (p < 0.05).
• All interfacial fracture toughness values were significantly lower than those of monolithic cement specimens.

Conclusions:

• The fracture toughness of luting cements is diminished by interactions with dentine.
• Cement-dentine interactions negatively impact the mechanical integrity of thin cement layers.
• These findings have implications for the selection and clinical performance of dental luting cements.